1. Field of the Invention
The present invention relates to oil well pumping units, and more particularly to hydraulically operated pumping units of the reciprocal kind.
2. Description of the Prior Art
Most commonly, extraction of underground oil is achieved by way of the walking beam pump system. This system, while mechanically large, provides one of the more accepted techniques in the art. In the recent past, however, various other techniques have been developed, including techniques in which hydraulic power is utilized to reciprocate the pump. For example, in my prior U.S. Pat. No. 3,782,117, I have set out a vertical, hydraulically operated, pumping system useful in oil well applications. The advantages of hydraulic power have thus been recognized, such systems providing the convenience of compact size as well as the convenience of shaping the power stroke to obtain optimum efficiency. Because of some frictional losses during the stroke and the drop-off in efficiency of hydraulic system with volumetric ratio such hydraulically operated pumping units often utilized pulley multiplication in order to obtain the stroke length necessary for extracting oil with reduced piston motion. This pulley multiplication heretofore has required large support structures which, similar to the walking beam pumps, presented an undesirable feature in the otherwise uninterrupted landscape. Furthermore the deployment of an oil well is typically vertical and consequently the stroke requirements are vertical, once more necessitating large vertical structures in the past.
It bears emphasis that the reciprocal motion of the pump can be exchanged into stored energy with the result that only the power necessary to lift the underground fluid is the power demanded on the system.